The invention relates generally to digital video processing and more specifically to a method and apparatus for inserting a compressed digital advertisement video into a compressed digital program video.
In modern television programming, it is desirable to seamlessly insert advertising information into a program video such that a viewer does not observe unsightly artifacts or other anomalies on a television screen when the program transitions into an advertisement or vice versa. The process by which advertisement is spliced into a program video is known as “ad insertion”. Conventionally, ad insertion is typically achieved by merging an analog advertisement video into an analog program video (which is also known as a “digital-into-analog” process). This insertion technique works by switching between (advertisement and program) video sources and broadcasting the multiplexed video to the viewer. If the advertisement is stored in a digital format, it is typically converted into an analog advertisement video prior to the ad insertion. Frame synchronization is typically a major concern in such an analog-based system, and other issues are not quite as critical. Since the video signal being broadcast is analog, the ad insertion equipment produces the multiplexed video in analog format regardless of whether the advertisement is stored in analog or digital format.
As television transmission systems switch to compressed digital formats, the need to insert advertisement using a “digital-into-digital” process becomes obvious. The digital-into-digital process achieves ad insertion by switching between compressed advertisement and program video streams and broadcasting the multiplexed output video stream to the viewer. Conventional solutions for the digital-into-digital process, however, are fraught with problems since video compression schemes such as the ones defined by the Moving Pictures Expert Group (MPEG) standard focuses mainly on the relationships between frames of video and packets of audio.
Splicing in the compressed digital domain to achieve ad insertion generally cannot be accomplished with the same degree of freedom as in the analog domain or in the uncompressed digital domain. The profile (or characteristics, which typically include the bit rate) of a compressed video stream continually changes over time depending on the contents of the video, the parameter values used to encode the video, and other factors. Unless care is taken to ensure that the splicing is accomplished at the proper points within the compressed video stream and with matched encoding profiles for the compressed streams to be merged, various unsightly artifacts or other anomalies can result in the multiplexed output video. Such artifacts and anomalies may include, for example, severe macroblocking, dropped frames, macroblock panics, audio glitches, pop gargling noises, drop outs, and so on.
Therefore, digital-into-digital ad insertion techniques that seamlessly merge compressed digital advertisement video into compressed digital program video are highly desirable.